1. Field of the Invention
The present invention relates generally to the field of lead-acid storage batteries and more particularly to thin, bipolar lead-acid batteries. Still more specifically, the invention relates to the assembly of such a battery in a manner which permits venting of gases evolved during formation and overcharge and, simultaneously, provides a means for introduction of electrolyte to the battery cells.
2. Background Art
Bipolar batteries are known to the art and consist generally of a positive plate, a negative plate and a separator, with substrates employed if multiple cells are used, to permit electron flow through the substrate. It has been attempted to combine several of the flat cells into multicompartment batteries encased in a suitable container.
In Koike, et al, U.S. Pat. No. 4,664,994 issued May 12, 1987 for "Enclosed Lead Storage Battery And Process For Producing The Same", a plastic film enclosure is provided around an entire cell by heat sealing a plastic film around the edges. Special provisions are made for sealing the film to the collector tabs. A safety valve is provided in the Koike, et al system by not sealing a certain area of the plastic film, whereby gas escape from within the cell is permitted, while oxygen or moisture introduction into the cell is prevented by the film to film contact in the area of the safety valve. A multiple cell structure showing the same type of individual cell wrapping, with collection of current occurring through contacts between tabs is shown in Suzuki U.S. Pat. No. 4,659,636 issued Apr. 21, 1987 for "Sealed Storage Battery".
Certain primary flat plate batteries having multiple layers and peripheral seals are shown in U.S. Pat. No. 3,784,414 issued Jan. 8, 1974 to Macaulay, et al for "Battery Sealant Carrier Having Adhesive Patches Impregnated Therein And A Method For Making It"; U.S. Pat. No. 3,964,932 issued to Oltman, et al on June 22, 1976 for "Battery Having Deformations In A Metal Layer"; U.S. Pat. No. 3,997,365 issued Dec. 14, 1976 to Feldhake for "Battery Having Polyamide Hot Melt Adhesive Seal". These latter patents do not describe any type of valve for permitting gas release, or for that matter, any charging technique which would lead to gas evolution. See also U.S. Pat. No. 4,275,130 issued June 23, 1981 to Rippel, et al for "Bipolar Battery Construction". The construction proposed does not use a venting arrangement as described herein.
It is desirable to provide multicell, bipolar batteries which are compact, which are rechargable and which are safe from the standpoint of having a gas release safety valve. As the design of such lead-acid, bipolar cell units approaches smaller and smaller dimensions, it will become increasingly difficult to provide an effective safety valve in the thin cells. It would represent a substantial improvement to this art if cell vent safety valves could be provided in a dimensionally effective and reliable manner.